CROSS REFERENCE(S) TO RELATED APPLICATIONS
This application claims the benefit under 35 U.S.C. Section 119 of Korean Patent Application Serial No. 10-2011-0055710, entitled “Ultrasonic Sensor” filed on Jun. 9, 2011, which is hereby incorporated by reference in its entirety into this application.
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OF THE INVENTION
1. Technical Field
The present invention relates to a sensor, and more particularly, to an ultrasonic sensor capable of measuring a distance to objects to be measured by generating an ultrasonic wave using a piezoelectric element and using time consumed to return the generated ultrasonic wave reflected from the objects to be measured.
2. Description of the Related Art
As an ultrasonic sensor, two types such as a piezoelectricity type and a magnetostriction type have been generally used. The piezoelectricity type means a type using a phenomenon of inducing voltage when pressure is applied to objects such as crystal, PZT (piezoelectric material), piezoelectric polymer, or the like, and to the contrary, inducing vibrations when voltage is applied thereto. On the other hand, the magnetostriction type means a type using a Joule effect (a phenomenon generating vibrations when applying a magnetic field) and a Villari effect (a phenomenon generating a magnetic field when applying stress) that are shown on an alloy of iron, nickel, and cobalt, or the like.
An ultrasonic element may be referred to as an ultrasonic sensor and an ultrasonic generator. The piezoelectricity type senses the ultrasonic wave using voltage generated when ultrasonic vibrations are applied to the piezoelectric element and generates the ultrasonic wave by vibrations generated when voltage is applied to the piezoelectric element. The magnetostriction type generates the ultrasonic wave by the Joule effect and senses the ultrasonic wave by the Villari effect.
Currently, the ultrasonic sensor generally used is operated by the piezoelectricity type using the piezoelectric element and has a structure in which the piezoelectric element is seated in a case and the ultrasonic wave generated from the piezoelectric element is discharged to the outside through the case.
Further, since the sensitivity of the piezoelectric element is changed according external temperature, a temperature compensation capacitor for compensating for the change in sensitivity is disposed in the case and the substrate for fixing the temperature compensation capacitor is mounted therein. The substrate serves as a terminal of a wire connecting the piezoelectric elements with the temperature compensation capacitor, or the like.
In addition, a sound absorbing material for absorbing vibration energy of the piezoelectric element to shorten reverberation time and protect internal parts is disposed in the case. The sound absorbing material is generally used as a nonwoven fabric.
As described above, the ultrasonic sensor has various parts disposed therein, wherein each part is electrically connected to the wire through the substrate.
However, since the substrate and the temperature compensation capacitor fixed to the substrate are disposed at a portion that is difficult to handle the equipment, it is difficult to mass-produce and automatically produce the ultrasonic sensor.
In addition, the sound absorbing material for shortening the reverberation time reduces vibrations of the piezoelectric element and thus, the vibration force of the piezoelectric element is weak. Therefore, since the intensity of the ultrasonic wave generated from the piezoelectric element is weak, the sensed distance of the ultrasonic sensor may be reduced.
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OF THE INVENTION
An object of the present invention is to provide an ultrasonic sensor capable of improving a vibration force of a piezoelectric element while increasing a sensed distance without using a substrate for fixing a temperature compensation capacitor.
According to an exemplary embodiment of the present invention, there is provided an ultrasonic sensor, including: a conductive case having a groove disposed at a bottom surface thereof; a piezoelectric element inserted into the groove and fixed to the groove by a conductive adhesive; a temperature compensation capacitor disposed on a top of the piezoelectric element, electrically connected to the piezoelectric element, and fixed to the case by a non-conductive adhesive; a first lead wire lead-in from an outside of the case and electrically connected to one surface of the temperature compensation capacitor and the case; and a second lead wire lead-in from the outside of the case and electrically connected to the other surface of the temperature compensation capacitor.
The piezoelectric element and the temperature compensation capacitor may be electrically connected to each other by conductive adhesive.
The conductive adhesive electrically connecting the piezoelectric element to the temperature compensation capacitor may be connected to an edge of the piezoelectric element.
The piezoelectric element and the temperature compensation capacitor may be electrically connected to each other by a wire.
The wire may be connected to the edge of the piezoelectric element.
The ultrasonic sensor may further include a sound absorbing material disposed on the top of the temperature compensation capacitor.
The ultrasonic sensor may further include a molding part filled in the case.
BRIEF DESCRIPTION OF THE DRAWINGS
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FIG. 1 is a perspective view of an ultrasonic sensor according to an exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line A-A′ shown in FIG. 1.
FIG. 3 is a partially enlarged view of portion B shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, the exemplary embodiments are described by way of examples only and the present invention is not limited thereto.
In describing the present invention, when a detailed description of well-known technology relating to the present invention may unnecessarily make unclear the spirit of the present invention, a detailed description thereof will be omitted. Further, the following terminologies are defined in consideration of the functions in the present invention and may be construed in different ways by the intention of users and operators. Therefore, the definitions thereof should be construed based on the contents throughout the specification.
As a result, the spirit of the present invention is determined by the claims and the following exemplary embodiments may be provided to efficiently describe the spirit of the present invention to those skilled in the art.
FIG. 1 is a perspective view of an ultrasonic sensor according to an exemplary embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line A-A′ shown in FIG. 1, and FIG. 3 is a partially enlarged view of portion B shown in FIG. 1. Referring to FIGS. 1 to 3, an ultrasonic sensor 100 according to an exemplary embodiment of the present invention includes a case 110, a piezoelectric element 120, a temperature compensation capacitor 150, a first lead wire 160, and a second lead wire 165.